Another thing is that views more and more symbolic borders for zoo enclosures. Of course, not for elephants or bears or big cats but Lota Deitrich, the sometimes director of Hanover Zoo, developed dry moats for antelopes. And he made trials. If the moats were more than 1.2 meters, the animals jumped down and grazed in the moat. If the moats were smaller than 1.2 meters, they jumped over. But with moats of 1.9 meter, the animals stayed in their enclosure. Also, it is well-known, even in Hanover, that they can jump maybe 10 meters or 12 meters. But they consider their exhibit as their territory.
